Logging Evaluation of Reservoir Characteristics of the Gu‐1 Member Sand‐Conglomerate in the Cretaceous Guyang Formation, Hetao Basin, China

ABSTRACT Sand‐conglomerate reservoirs in the Cretaceous Guyang Formation of the Hetao Basin have recently demonstrated significant exploration potential. However, their strong heterogeneity and complex pore‐throat architecture pose considerable challenges for reservoir evaluation. This study focuses on the Lower Cretaceous Gu‐1 Member in the southwestern Linhe Sag, developing an effective well‐log evaluation methodology through integrated core observation, experimental testing and log analysis. Methodologically, we established novel multi‐parameter lithology identification parameters X and Y (derived from natural gamma ray, compensated density, compensated neutron and spontaneous potential logs). This method achieves a lithology identification accuracy of over 90%, creating a lithology identification chart that efficiently discriminates complex lithologies from conglomerate to siltstone—simplifying the traditionally cumbersome interpretation process. For petrophysical evaluation, multiple linear regression porosity models were developed specifically for Oil Groups I and II, enhancing the interpretation accuracy by over 15% compared to conventional single‐log methods. Critically, we systematically identified and characterised four types of barriers and interbeds (argillaceous, calcareous, gravelly and petrophysical)—the first comprehensive classification for this reservoir type—with their corresponding log‐response features clarified. For fluid identification, we innovatively combined radial investigation characteristics of array induction resistivity (revealing distinct separation patterns for oil, water, oil–water and dry layers) with nuclear magnetic resonance differential spectrum and shifted spectrum analysis, enabling reliable fluid typing in lithologically complex intervals. Through integrated analysis of lithology, petrophysical properties, barriers/interbeds, and fluids, precise evaluation of effective reservoirs was achieved, with the porosity cutoff determined as 9% and permeability cutoff as 0.1 mD. This work provides reliable technical support for exploring highly heterogeneous sand‐conglomerate reservoirs in the Hetao Basin and analogous regions.